Testing to evaluate the potential of a new well or field is a common practice in the oil and gas industry. When performing this task in a deep-water environment, however, there are significantly more challenges for the operator and service company to address, and when testing a heavy oil reservoir, the challenges are even further exacerbated. Special consideration must be given to the following issues: 1. High rig rates associated with deep-water operations will make job problems more costly. 2. Producing heavy crude oil to surface, moving it through the surface production train, and finally, disposing of it in an environmentally acceptable manner. 3. Deep-water environment exposes the crude to an extended period of heat loss and low temperatures while it is in the landing string.In order for the well test to be effective, all the above conditions must be fully understood and methodology employed that will reduce the chance that operational risks will occur. This paper will discuss the successful testing of a heavy oil reservoir in deep water. A number of different ways to assist the production of heavy crude in the deep-water environment will be presented, and the relative merits and limitations of each will be considered. The discussion will provide an outline of the necessary additions to the surface production train and the use of chemicals and heat to ensure flow. Finally, it will consider what equipment is necessary to properly dispose of the produced fluid.The testing methods discussed in this paper can be applied to heavy-and low-pour-point crudes in deep water. The equipment and methods can also be used in shallow water applications or on land. The case history data will illustrate: 1. Why particular methods and equipment were used and why others were rejected.
Proposal Testing to evaluate the potential of a new well or field is a common practice in the oil and gas industry. When performing this task in a deep-water environment, the operator and service company must address the special needs of the testing environment, and when testing a heavy oil reservoir, the challenges are even further exacerbated. Special consideration must be given to the following issues:High rig rates associated with deep-water operations will make job problems more costly.Producing heavy crude oil to surface, moving it through the surface production train, and finally, disposing of it in an environmentally acceptable mannerExposing the crude to an extended period of heat loss and low temperatures while it is in the landing string. In order for the well test to be effective, all the above conditions must be fully understood and methodology employed that will reduce the chance that operational risks will occur. This paper will discuss the successful testing of a heavy oil reservoir in deep water. A number of different ways to assist the production of heavy crude in the deep-water environment will be presented, and the relative merits and limitations of each will be considered. The discussion will provide an outline of the necessary additions to the surface production train and the use of chemicals and heat to ensure flow. Finally, the paper will consider what equipment is necessary to properly dispose of the produced fluid. The testing methods discussed in this paper can be applied to heavy- and low-pour-point crudes in deep water. The equipment and methods can also be used in shallow water applications or on land. The case history data will illustrate:Why particular methods and equipment were used and why others were rejected.The success of the methods selected to address the testing needs.What conditions are inherent when testing deepwater reservoirs in heavy oil, and what is required to nullify or reduce the impact from these conditions on testing operations.The lessons learned from the jobs. Improvements that could be made to further facilitate testing of heavy oil in a deep-water environment.How careful planning can overcome the testing problems in deep water for both low- and heavy-pour-point oils. The information will show that employing proven methods and the proper equipment enables successful testing with reduced risk in difficult heavy- and low-pour- point reservoirs. Introduction For purposes of this paper, heavy oil is defined as any petroleum with an API gravity of less than 20 degrees or a high specific density. In many cases, this type of crude will contain significantly large amounts of impurities and will have constricted flow properties due to its inherent high viscosity. Waxes often are a significant component and contribute to difficulties in flow. Production of heavy or low-pour-point oils typically is more difficult and more expensive than with lighter oils. This fact is particularly true when it comes to short-term, temporary operations such as well testing. Well testing in deep water exposes produced crude to a long period of time in a low-temperature environment that starts at the seabed and extends to the rig-mounted surface production package. Water temperature at the sea floor is often in the 35° F range. In addition, space constraints on exploration rigs may impact the configuration, size, and volume of the production equipment that is selected. A further complication is the fact that many of the reservoirs in this category are also unconsolidated. The difficulties associated with testing these wells can be divided into three broad categories:Flowing or producing the wellSeparating the fluids and measuring the flow ratesDisposing of produced fluid. There are other issues that do not really fall into these categories, but because of their significance, they will be discussed also.
Well testing operations in challenging environments are becoming more common, and as a result, testing technologies have had to continually improve or develop newer techniques that can meet the more corrosive needs in the new areas. These testing methods must not only achieve operational efficiency, increase personnel safety and protect the environment, they must address additional challenges in the new environments where current development is taking place. In spite of the ongoing improvements, however, there are still scenarios that remain problematic, and one the most challenging continues to be the production and well testing of heavy-oil reservoirs in sandstones or carbonates. This is particularly true when testing operations are performed offshore. Heavy oils normally are defined as those with an API gravity below 20 degrees with very high viscosities, a variable that is a major factor in determining the flowing capacity of oil through the reservoir, the completion string, and surface facilities. Pressures and low temperatures can increase the viscosity of the oil to an even higher value, depending on the wellbore characteristics, geographical area, and the PVT properties of the crude. While most onshore reservoirs are produced using cold production or steam injection to reduce the viscosity, offshore environments present more difficult scenarios due to the low temperatures at the sea bed and in the ocean thermo-cline regions which further complicate the typical complexity of all operations in this type of environment. Enhanced simplicity and reliability is critical in offshore development because of the increased intervention cost compared to the cost of onshore cases and the need to maintain environmental safety. Thus, careful initial planning of these operations remains paramount. This paper reviews experiences that have occurred while testing heavy-oil reservoirs using a wide range of equipment configurations and procedures. The authors feel that this information will be extremely valuable for operators and service personnel who are planning well testing operations offshore.
When well testing is conducted, the reservoir response during the initial surge to stable drawdown and pressure buildup will define productivity expectations for a new well. The quality of the reservoir fluid samples further defines the value of the reservoir assets. To ensure that operations will be conducted safely, rig-time efficiency will be maximized, and the overall well test objectives will be met, several critical well testing decisions must be made. This paper describes the value of real-time access to reservoir information and tools to control well testing operations. Also described is a system that has been used to provide immediate access to the reservoir through the use of wireless downhole telemetry, data acquisition and control, and instantaneous visibility of data from any location around the world. While the idea of providing access to some reservoir information in near real time is not a new concept, the system described is not dependent on formation geology and is the only one with the capability to provide access to all reservoir information in real time, perform analysis using this information, and control well testing operations remotely with the click of a mouse button. Case histories will be presented to demonstrate the capabilities of the system described.
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